It may be normal to have cramps during pregnancy. Some more common causes are things like dehydration, movement of the baby and sex, which can all lead to occasional cramping. However you need to notify your doctor right away with any cramping that doesn’t let up and any cramping that associated with bleeding.
This could be a signal for a miscarriage, premature labor, and actually labor. If your cramping becomes regular and or you notice a regular pattern, call your doctor right away.